1. Field of the Invention
This invention concerns an improvement related to an underground tank leak detector instrument. More particularly, the instrument deals with measuring the level of liquid in an underground tank. And, it employs some aspects of a manometer for measuring the change in liquid level.
2. Description of the Prior Art
An instrument has been developed for measuring a change in surface level of a liquid, and the adaptation of that instrument to underground tank leak detection of petroleum products has been quite successful in connection with underground tanks holding gasoline. However, when attempts were made to make use of that instrument for the same measurements where the product in the tank was diesel fuel, a problem was encountered in connection with the open end of a leg of the manometer portion. An embodiment of the foregoing instrument is shown and described in an article published in the "Petroleum Marketer," September-October 1978 issue, Volume 46, No. 5. That published article clearly illustrates a form of structure to which this invention applies.
Thus, it is an object of this invention to provide apparatus for overcoming a difficulty which causes failure in the operation of an instrument which includes a manometer or the like, containing an indicator fluid in a U-tube with one leg open and subject to being immersed in a liquid being measured.